Display devices which are capable of automatically orienting a displayed image to a landscape orientation or a portrait orientation based on an sensed physical orientation of the display device's screen are known. For example, U.S. Publication No. 2004/0201595 A1 discloses a self-orienting display which automatically rotates and reformats a display image in accordance with the “sensed characteristics of an object”, which include the sensed orientation of a display. The publication teaches that sensing of object characteristics may be achieved by way of various types of sensors, such as mechanical, electrical, optical, acoustic or gyroscopic sensors, or combinations thereof. In other examples, U.S. Publication Nos. 2003/0222848 A1 and 2003/0122781 A1 also disclose a method, system and/or apparatus for automatically switching viewing orientations of a display in response to physical rotation of the display. The specific mechanisms for communicating sensed screen orientation to hardware or software responsible for automatically orienting a displayed image are not described in detail.
Known analog or digital display devices, such Cathode Ray Tubes (CRTs), flat panel displays such as Liquid Crystal Display (LCD) or Digital Light Processing (DLP) monitors, or plasma displays for example, are often driven by a graphics subsystem (GSS) of a host device to which the display device is connected. The host device may be a “CPU box” or “tower” of a computer for example. The graphics subsystem is a component which converts a logical representation of an 2D or 3D image stored in memory to signals that can be used by a display device to generate and display the image. A GSS may either be integrated into the motherboard of a host device or it may be a stand-alone expansion card having a dedicated processor (the dedicated processor may be referred to as a Graphics Processing Unit or GPU). Examples of commercially available of GSSs are the Radeone® X800, Radeon® X800 Pro, and Radeon® X600 cards manufactured by ATI Technologies Inc. Graphics subsystems may be referred to in the art by various terms, such as a graphics cards, video cards, video boards, video display boards, display adapters, video adapters, or graphics adapters.
In many contemporary systems, the interconnection between a GSS and display device takes the form of a cable which conforms to a known industry standard, such as a Digital Visual Interface (DVI), High Definition Multimedia Interface (HDMI), VGA, composite/S-video or component out. Alternatively, a proprietary form of interconnection could be employed. For the most part, the signals that are transmitted across the cable, which may be analog or digital depending upon the standard governing the interconnection and the type of signals supported by the display device, flow from the GSS to the display device. However communication in the reverse direction may also occur in some cases. For example, communication in the reverse direction may occur soon after a display device is connected to a host device, for purposes of sending information from the display device to the host device regarding display device characteristics.
A novel approach for notifying a graphics subsystem of a physical change at a display device would be desirable.